Multi-site atrial pacing, for example bi-atrial pacing, is a known method of reducing the incidence of atrial tachyarrhythmias. In this pacing mode, atrial pacing electrodes are located at two sites within the atria. In response to sensing an atrial depolarization at one site, pacing pulses are delivered either to both sites or to the site at which the depolarization was not sensed. In the context of this pacing mode, the issue of whether to provide a pacing pulse or pulses in response to a sensed atrial premature depolarization, also referred to as a premature atrial contraction (PAC) has arisen, as in some cases pacing pulses synchronized to PACs can be pro-arrhythmic.
The issue of the possible pro-arrhythmic effect of PAC synchronized atrial pacing pulses is dealt with in the article “Multisite Pacing for AF management—Technical and Clinical Challenges”; Mehra, et al., Journal of Interventional Cardiac Electrophysiology, 2000; 4:69-79, incorporated in its entirety by reference herein. In this article, it is proposed that pacing pulses should not be delivered synchronized to PACs occurring at short coupling intervals from previous atrial depolarizations, but should be delivered synchronized to PACs having longer coupling intervals. An exemplary pacemaker for accomplishing this result is disclosed in U.S. Pat. No. 5,403,356, issued to Hill, et al., also incorporated herein by reference in its entirety. In this patent, a defined “APB interval” following an atrial depolarization is defined by the pacemaker. Non-refractory sensed PACs within this interval do not trigger synchronized pacing pulses. PACs sensed outside this interval do. In the particular embodiment disclosed in this patent, the duration of the APB interval varies as a result of sensed atrial rate. Automatic adjustment of anti-arrhythmia pacing modes and parameters generally is disclosed in U.S. Pat. No. 6,185,459, issued to Mehra, et al., also incorporated herein by reference in its entirety.